1. Field of the Invention
The present invention relates to a device for storing compressed gas, having a plurality of storage containers which each have a container wall which surrounds a cavity provided for storing the compressed gas, the storage containers one conductively connected to one another and each storage container has a head piece which is connected to the container wall, and at least one connection for introducing and/or discharging the compressed gas.
2. Discussion of the Prior Art
Gases are conventionally transported in special containers which firstly prevent the gases from evaporating and secondly have to be of sufficiently stable design that the gas cannot be suddenly released in the event of the container being damaged. Furthermore, these containers, if they are used for example for storing gases at high pressure, have to have an extremely firm and stable container wall. Containers of this type for compressed gas conventionally consist of steel or of another metal. In this case, for reasons concerned with strength, either spherical shapes or cylindrical shapes are preferred. However, containers of this type have the disadvantage firstly of having a very high dead weight even when empty. Furthermore, the quantity of gas which can be stored is severely restricted by the existing geometry of the container.
With regard to increasing the quantity of gas which can be stored, U.S. Pat. No. 5,577,630 discloses a pressure container which is used for storing natural gas. This container consists of a row of elongated storage elements which consist of plastic and are arranged next to one another. In this case, the storage elements are mutually supported via the touching walls. The storage structure has a woven fabric wrapped around it in order to increase the strength of the container. By arranging a plurality of storage elements next to one another a single pressure container is provided which, in contrast to the previously conventional, cylindrical pressure containers, is able to hold a substantially greater quantity of compressed gas. Since, however, the individual storage elements are surrounded by a single covering layer, it is not possible for the container to be individually adapted in its geometrical shape to different requirements. Furthermore, the known container has the disadvantage that in the event of damage to a single storage element the entire container has to be replaced. 
Furthermore, gas-transporting vehicles are known where compressed gas is stored in large, bottle-like containers which are arranged lying parallel to one another and can communicate with one another at their end sides through corresponding connecting conduits. The individual containers, which are formed from steel pipes, can have a fiber material wrapped around their cylindrical part in order to increase the strength and are held together by an external supporting frame.
Starting from the above-mentioned prior art, the present invention is based on the object of developing a device for storing compressed gas in such a manner that the disadvantages mentioned in the prior art are avoided. In particular, the intention is to provide a device for storing compressed gas which firstly has sufficient strength with regard to the gas to be stored and which secondly can be adapted individually in its geometrical structure to the available space and to the quantity of gas to be stored.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a device for storing compressed gas, which device includes a plurality of storage containers which each have a container wall that surrounds a cavity in which the compressed gas is stored. In the gas storage facility according to the invention, each storage container has a head piece which is connected to the container wall. The storage containers are connected or can be connected to one another mechanically and in a modular manner to form a compact constructional unit via the respective head pieces arranged directly next to one another in a row. The head pieces are therefore in mutual contact. In order to increase the strength or to protect the gas storage facility, it is advantageous if each of the storage containers has an additional covering layer which is arranged on the container wall at least in partial regions of the particular storage container.
This results in the provision of a device for storing compressed gas which can be matched individually to the most varied requirements. The device can be expanded or reduced by an appropriate number of storage containers depending on the quantity of gas to be stored. As a result, not only can the quantity of gas to be stored be varied, but it is also possible to adapt the device to the available space. The individual storage containers can namely be arranged both next to one another and above one another, with the result that the geometry of the device which is provided can deviate altogether from the previous spherical or cylindrical configurations.
Should one of the storage containers be damaged during use of the device and therefore have to be replaced, the corresponding storage container can be removed from the entire device and replaced by a new storage container. Replacement of the entire device can therefore be avoided This results, inter alia, in a considerable reduction of costs. Furthermore, it is possible for the device to continue to be used during replacement of the damaged storage element if appropriate shut-off valves are provided. This leads to a reduction in the down times of the installations operating using the device.
In order to obtain storage containers having particularly high strength, the covering layer can be arranged on the outer surface of the container wall. However, it is also possible for the covering layer to be arranged on the inner surface of the container wall or within the container wall. Of course, particularly if a plurality of covering layers are used, it is also possible for the various options of arranging the covering layer/covering layers to be combined.
For example, the container wall may be of single-part or multipart design. However, in the case of the multipart configuration of the container wall, it has to be ensured that the individual parts are suitably connected to one another in a gastight manner.
The individual storage containers can be produced in a simple and cost-effective manner and connected to one another in just as simple a manner, which results in a high saving on costs during the production of the device according to the invention.
According to the invention, the head piece can be connected to the container wall by bonding, preferably by means of soldering or welding. Of course, other forms of connection are also conceivable; it is merely important for the head piece and the container wall to be connected to one another in a gastight manner and, depending on the permissible gas pressure, in a sufficiently resistant manner to shearing and extension.
In a further refinement, the storage containers can be of cylindrical design. The cylindrical shape of the container wall provides optimum strength properties with regard to the prevailing expansion pressure of the stored gas. In an expedient refinement, a storage container may, for example, have an internal diameter of 56 cm and an external diameter of 60 cm.
In a further refinement, a storage container has a conical cross-sectional tapering in its end region used to hold it in the head piece. It is advantageous for the side walls of the head piece, which are in contact with the cross-sectional tapering of the storage container, to be of corresponding design. This results in a further improvement in the strength of the connection between the head piece and the container wall. Furthermore, the cross-sectional tapering of the ends of the container wall enables the storage containers to be packed particularly densely within the device.
In another embodiment, connecting elements are provided for connecting the storage containers. The connecting elements can preferably be of rod-shaped design. For examplexe2x80x94but not exclusivelyxe2x80x94it is possible for the connecting elements to have the function of tension rods and to be designed as threaded rods or expansion screws. This makes it possible to connect the storage containers releasably to one another via the head pieces.
In a further embodiment each of the head pieces has at least one, preferably two openings for holding the connecting elements. In this case, the diameter of the openings advantageously approximately corresponds to the outer diameters of the connecting elements. The at least one opening expediently extends continuously over the entire width of the head piece. As a result, a common connecting element can be used for the connection of the individual storage containers. The connecting element is passed through all of the head pieces, so that the head pieces, particularly if two openings in each case are provided, can be oriented such that they are aligned and in a straight row next to one another. This is particularly advantageous ifxe2x80x94as is explained in detail belowxe2x80x94the head piece is provided with a flow duct through which the compressed gas is guided after it has emerged from the cavity of the storage container. In this case, it is particularly important, in order to form a uniform flow duct, for the head pieces not to be displaced with respect to one another.
When a connecting element, for example a threaded rod, passing through all of the head pieces is used, suitable fastening elements can be provided in the region where the connecting element emerges from the outer head pieces in each case. Examples of suitable fastening elements are nuts or the like.
If, for example, a damaged storage container is to be replaced, the fastening elements are released from the connecting element enabling the individual storage containers to be separated from one another. The damaged storage container can then be replaced within a very short time by a new storage container. The individual storage containers are pushed together again and connected securely to one another via the fastening elements.
It is possible in principle to connect the storage containers to one another by separate pipelines. However, it can be particularly advantageous, as has already been described above, to provide a flow duct for passing the compressed gas through in the head piece. This flow duct extends continuously over the entire width of the head piece. It is used for conducting away the gas emerging from the storage containers and has, in a preferred embodiment, an internal diameter of approximately 8 mm. However, the invention is not restricted to the use of specific diameters for the flow duct.
According to the invention, the flow duct can have a respective sealing element in the end-side end regions of the head piece. A sealing element of this type, which may for example be an O-ring or the like, is used for connecting the individual head pieces to one another in a gastight manner, particularly in the region of the flow duct. The flow duct can communicate with the cavity of the storage container via a hole.
A valve, preferably a nonreturn valve, can advantageously be arranged in the hole. The valve can take on the function of a restrictor or a flow controller. This is particularly of advantage if the storage container is damaged. Gas which flows from the remaining storage containers into the flow duct is thereby prevented from being able to emerge from the device via the damaged storage container. For this purpose, in normal operation of the device the valve is open on account of the high gas pressure prevailing in the storage container. If the storage container should, for example, burst open or be damaged in another manner, the valve is closed on account of the falling pressure in the storage container and of the gas pressure prevailing in the flow duct. The gas stored in the other storage containers is therefore unable to escape, and in spite of the damaged storage container the device can also continue to be used.
In a further refinement, at least one of the head pieces can have a connection opening. A plurality, for example, of storage containers connected in a row can be connected to other rows of storage containers via such a connection opening. Because of the corresponding connection opening, an arrangement of the storage containers next to one another and also above one another is therefore possible.
According to the invention, the storage container can have a cover element at that end of the container wall which is opposite the head piece. The cover element, which preferably consists of the same material as the head piece, can likewise be connected to the container wall by welding, soldering or the like. Of course, other types of connection are also conceivable here; the important thing again is for the cover element to be connected to the container wall in a gastight manner and, in the direction of the longitudinal axis of the container, in a manner which is resistant to extension.
In a preferred design, the head piece and/or the cover element can consist of metal, preferably of cast material. In particular, precision castings can be used as the material.
According to the invention, the container wall can be formed from a material which is suitable in particular for absorbing forces in the longitudinal direction of the storage container. The container wall can preferably be formed from metal, plastic and/or a fiber composite material.
The container wall may, for example, be formed from polypropylene, in particular from polypropylene having long fibers. In this case, the fibers of the polypropylene are preferably oriented in the direction of the longitudinal axis of the container. Of course, the container wall may also consist of other materials. In this case, particular care should be taken to ensure that the material is as gastight as possible, i.e. does not allow any significant diffusion of the gas to be stored through the container wall. If fiber composite materials are used for the container wall, these may contain, for examplexe2x80x94but not exclusivelyxe2x80x94glass fibers, aramide fibers, boron fibers, organic polymer fibers, carbon fibers or other types of fiber. The only important thing is for the fibers to have sufficiently high strength in order to be able to withstand the expansion pressure of the gases stored in the container. If a metal is used for the container wall, preference is given here to steel, in particular ST 52.
In a further embodiment of the invention, the container wall can be reinforced by an additional covering layer of a material which is suitable in particular for absorbing forces in the circumferential direction of the storage container. Materials of this type are preferably plastic and/or fiber materials. Examples which can be mentioned of further preferred materials are the materials described with regard to the gastight container wall. The covering layer itself does not need to be gastight.
The gases to be stored may, for example, be gaseous fuels, such as natural gas or hydrogen, or air, oxygen, nitrogen or else technical gases or the like. The invention is not restricted to any particular type of compressed gas.